Long-wavelength UV-LEDs and charge management in the detection of gravitational waves in space

Yun Kau Lau^1,2*Yuandong Jia³Yinbowen Zhang³Suwen Wang⁴Guozhi Chai³Zhang Zemin³Yi Zhang³Hongxin Li³Shuanglin Huang⁵Hongqing Huo³Zongfeng Li⁶

• ¹Chinese Academy of Sciences (CAS), Beijing, China
• ²Chinese Academy of Sciences Academy of Mathematics and Systems Science, Beijing, China
• ³Lanzhou University, Lanzhou, China
• ⁴Hainan Tropical Ocean University, Sanya, China
• ⁵Beijing Institute of Mathematical Sciences and Applications, Beijing, China
• ⁶Chinese Academy of Sciences Technology and Engineering Center for Space Utilization, Beijing, China

For the charge management system in gravitational wave detection missions, a continuous discharge strategy is considered by continuously illuminating a test mass (TM) with weak light in such a way to strike a balance between the charging and discharging rates and at the same time avoids the requirement for frequent activation of charge measurements. Built on experiments by one of us Wang et al. (2022) based on a simple parallel plate model for inertial sensor, in the present work a more sophisticated inertial sensor model that mimics the surface properties and work function of a cubical TM of an inertial sensor in space (like that of the LISA Pathfinder) is employed to study bipolar charge management system that utilizes UV-LEDs with peak wavelengths of 269 nm, 275 nm, 280 nm, and 295 nm that are longer than the standard 255 nm commonly employed for direct TM illumination. Experimental results indicate that the 275 nm UV-LED achieves optimal performance, maintaining the TM potential closer to zero and at the same time accommodates both rapid discharge and continuous discharge strategies. The present work provides useful input in the future study of system design and optimization for the charge management system.